Other warnings from medical professionals: the recent editorial published in the Journal of the Society for the Study of Addiction, which cautions against drawing erroneous conclusions from population studies, and the editorial comment from the American Society of Addiction Medicine on February 20, 2018. And don't forget NIDA's rigorous study showing pot users are twice as likely to have abused opioids and have an opioid use disorder than non-marijuana users.
SAM has published a one-pager describing the overwhelming link between marijuana and opioid abuse. While not every marijuana user will go on to use heroin, nearly all heroin users previously abused marijuana. We need smart policies that discourage use, get people back on their feet, and restore people to participate in and contribute to society. States that have legalized marijuana, by contrast, see increased drugged driving, increased arrests of minority youth, and increased emergency room visits. Colorado's opioid deaths have doubled between 2011-15. Legalization is a failed experiment.
From a SAM e-mail.